Shapiro R, Vallee B L
Proc Natl Acad Sci U S A. 1987 Apr;84(8):2238-41. doi: 10.1073/pnas.84.8.2238.
Human placental ribonuclease inhibitor (PRI) abolishes both the ribonucleolytic activity of angiogenin toward 28S and 18S rRNA and its angiogenic activity on the chicken embryo chorioallantoic membrane. Treatment of the angiogenin-PRI complex with p-hydroxymercuribenzoate releases enzymatically active angiogenin. Assays measuring competition between angiogenin and bovine pancreatic ribonuclease A for PRI reveal that binding of the inhibitor to angiogenin is extremely tight, with a Ki value well below 0.1 nM. The stability of the angiogenin-PRI complex was assessed by cation-exchange HPLC quantitation of free angiogenin. No significant dissociation was detected after 17 hr at 25 degrees C in the presence of a large excess of bovine ribonuclease, which serves as a scavenger for free inhibitor. The results of these experiments, based on the predictive capacity of the angiogenin/RNase homology, suggest that PRI and related inhibitors may participate in the in vivo regulation of angiogenin and that this might have pharmacologic and/or therapeutic implications.
人胎盘核糖核酸酶抑制剂（PRI）既能消除血管生成素对28S和18S rRNA的核糖核酸酶活性，也能消除其对鸡胚绒毛尿囊膜的血管生成活性。用对羟基汞苯甲酸处理血管生成素-PRI复合物可释放出具有酶活性的血管生成素。测量血管生成素与牛胰核糖核酸酶A对PRI的竞争作用的实验表明，该抑制剂与血管生成素的结合极其紧密，其Ki值远低于0.1 nM。通过阳离子交换HPLC对游离血管生成素进行定量分析，评估了血管生成素-PRI复合物的稳定性。在25℃下，存在大量过量的牛核糖核酸酶（作为游离抑制剂的清除剂）的情况下，17小时后未检测到明显的解离。基于血管生成素/核糖核酸酶同源性的预测能力，这些实验结果表明，PRI及相关抑制剂可能参与血管生成素的体内调节，这可能具有药理学和/或治疗学意义。
